Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease and Varicella Zoster Virus Infection - Frequency of an Association

To determine whether there is a correlation between myelin oligodendrocyte glycoprotein (MOG) antibody-associated diseases and varicella zoster virus (VZV) infection. We provide a case report and performed a study to determine the frequency of MOG antibodies (MOG-IgG) in neurological VZV infections. Patients admitted to the Medical University of Innsbruck from 2008–2020 with a diagnosis of a neurological manifestation of VZV infection (n=59) were included in this study; patients with neuroborreliosis (n=34) served as control group. MOG-IgG was detected using live cell-based assays. In addition, we performed a literature review focusing on MOG and aquaporin-4 (AQP4) antibodies and their association with VZV infection. Our case presented with VZV-associated longitudinally extensive transverse myelitis and had MOG-IgG at a titer of 1:1280. In the study, we did not detect MOG-IgG in any other patient neither in the VZV group (including 15 with VZV encephalitis/myelitis) nor in the neuroborreliosis group. In the review of the literature, 3 cases with MOG-IgG and additional 9 cases with AQP4 IgG associated disorders in association with a VZV infection were identified. MOG-IgG are rarely detected in patients with VZV infections associated with neurological diseases.


INTRODUCTION
Varicella zoster virus (VZV) is an exclusively human neurotropic herpes virus, presents with chickenpox (varicella) as inaugural infection, and remains latent in the dorsal root ganglions, cranial nerves, and the autonomic nervous system, and upon reactivation, results in rash and pain in one or more dermatomes, known as shingles (herpes zoster). This would occur often decades after the primary infection, particularly in susceptible immunocompromised patients, and older patients due to immunosenescence (1).
However, until now, there has been no systematic analysis about the association of MOG-IgG and neurological manifestations of VZV infection. Here, we describe a patient with MOG-IgG positive VZV-associated longitudinally extensive transverse myelitis (LETM), perform a study to determine the MOG-IgG frequencies in patients with VZV infection and neurological involvement and present the results of a literature review.

Patients and Samples
The retrospective study included 59 patients who were admitted to the Medical University of Innsbruck between 2008 and 2020 with the diagnosis of a neurological manifestation due to VZV infection and had an available serum sample of at least 500 µl. Diagnosis of VZV infection with neurological involvement (i.e., meningitis, encephalitis, myelitis, encephalomyelitis, cranial nerve or/and segmental zoster paresis) was based on the presence of typical dermatomal rash followed by neurological symptoms and supported by laboratory findings (elevated CSF cell count, positive VZV DNA in the cerebrospinal fluid (CSF) as determined by polymerase chain reaction (PCR), or increased CSF VZV-IgG) (19,20). CNS involvement was defined as encephalitis or myelitis or a combination of both. In the absence of a typical rash, diagnosis was always based on a positive CSF VZV DNA and CSF pleocytosis.
Patients with neuroborreliosis [previously published (21)] were included as control group (n=34), as this is also a disease entity of infectious origin that might affect the CNS as well as the PNS, and also typically shows elevated CSF cell count and disrupted blood-CSF-barrier as indicated by elevated Qalb. In addition, there is no known association of neuroborreliosis with AQP4 or MOG antibodies. Briefly, these patients were admitted to Medical University of Innsbruck between 2009 and 2016 and received diagnosis of neuroborreliosis according to EFNS criteria (22). Diagnosis was based on typical neurological symptoms, appropriate routine CSF findings (pleocytosis, blood-CSF barrier impairment, and/or intrathecal synthesis of immunoglobulins), and intrathecal synthesis of borrelia-specific IgG antibodies [antibody specificity index (ASI) >1.5] (22).
Results of routine diagnostic procedures, clinical, magnetic resonance imaging (MRI), and CSF data were collected. Routine CSF work-up comprised red blood cell (RBC) and white blood cell (WBC) count, CSF total protein concentration, CSF/serum albumin quotient, and CSF and serum IgG, IgM, and IgA concentrations. Intrathecal synthesis of IgG, IgM and IgA were calculated by the Auer and Hegen formula (23) and expressed as percentage intrathecal fraction. IgG index was calculated as [CSF IgG/serum IgG]/[CSF albumin/serum albumin]. CSF was collected by lumbar puncture and blood by simultaneously peripheral venous puncture. Serum was isolated from blood by centrifugation after the blood samples were allowed to clot for ≥30 min. All samples were centrifuged at 2000 g for 10 min at room temperature.

MOG-IgG Assay
The presence of MOG-IgG was determined by live cell-based immunofluorescence assay with HEK293 cells transfected with full-length human MOG (alpha-1 isoform), as previously described (24). Screening for serum antibodies was performed at 1:20 and 1:40 dilutions by two independent investigators blinded for the clinical diagnosis. An isolated IgM reactivity was excluded by the use of heavy chain-specific secondary antibodies against IgG (Dianova, Hamburg, Germany) (24).

Ethics
The study was approved by the Ethics Committee of the Medical University of Innsbruck (approval number AM3041A). Written informed consent was obtained from all patients. Authorization has been obtained for disclosure (consent to disclose) from the index case patient.

Statistics
Statistical analysis was performed using SPSS 26.0 (SPSS Inc, Chicago, IL, USA). Non-parametric data were displayed as median and interquartile range. Categorical variables were reported as frequency and percentage. For group comparisons, Mann-Whitney-U and c 2 tests were applied, as appropriate. Twosided P-values <0.05 were considered statistically significant.

Literature Review
We conducted a literature search in MEDLINE and Google Scholar. Search terms were: VZV AND MOG or AQP4 or NMOSD or LETM; herpes zoster AND MOG or AQP4 or NMOSD or LETM. Abstracts that primarily did not deal with VZV infection and MOGAD or NMOSD or LETM were excluded. In addition, articles identified in reference lists of the individual papers were selected if considered appropriate. subsequent gait ataxia and neurogenic bladder disturbance requiring catheterization at our emergency department. Six days before the first neurological symptoms, the patient had developed herpes zoster infection (dermatome T6 right side) treated by his general practitioner with oral acyclovir (5 days, 3 x 1000 mg per day orally). There was no history of constitutional symptoms or a recent vaccination. A MRI of the spinal cord showed a T2 hyperintense lesion extending from T1 to conus medullaris confined to gray matter ( Figure 1) with only a very faint contrast enhancement, whereas brain MRI was normal. CSF analysis revealed lymphocytic pleocytosis with a WBC count of 101 cells/ml, and oligoclonal bands were negative. Despite the VZV DNA PCR results being negative, the CSF VZV antibodyspecific index (ASI) was highly elevated (9.4). However, in addition, MOG-IgG in serum were positive at high titer (1:1280), while AQP4-IgG were absent. Further diagnostic work-up to determine immune deficiency or a malignancy was negative (including a whole body 18F-fluorodeoxyglucose positron emission tomography-computed tomography, human immunodeficiency virus screening, serum immunoglobulin levels, flow cytometry of peripheral blood). MOG-IgG associated LETM following VZV infection was diagnosed, and the patient was treated with a combination of high-dose methylprednisolone (10 days: 1,000 mg for 3 days, 500mg for 4 days, 250 mg for 3 days) followed by oral tappering and intravenous acyclovir (3 x 750 mg for 10 days, 3 x 500 mg for 8 days followed by oral acyclovir 3 x 1000 mg for 5 days). Thereafter, no further disease-modifying or immunosuppressive therapy was started. After three months, the MOG-IgG titer had decreased to 1:320, and MOG-IgG was undetectable after another five months. Except for mild neurogenic bladder dysfunction, there was complete clinical and imaging remission without further relapses after an 18-month follow-up. EDSS improved from an initial score of 3.5 to 1.0 at 18-month follow-up.

Demographic, Clinical, and Main Cerebrospinal Fluid Characteristics
A total of 59 patients with neurological involvement due to VZV infection and 34 patients with neuroborreliosis were included into this study ( Figure 2). Demographic and main clinical

MOG-IgG in VZV Infection With CNS Involvement
All patientsthose with VZV infection with CNS involvement and those with neuroborreliosiswere negative for serum MOG-IgG. One patient with VZV infection and radiculitis had a borderline MOG-IgG positive titer of 1:160. This result was not confirmed by using heavy chain-specific secondary antibodies and was therefore regarded as negative.

Literature Review
We identified 2 case reports (15,25) and 1/10 patients in a case series (20) with MOG antibody-associated myelitis in association with a VZV infection; in addition, there are 9 reports of AQP4 antibody-associated CNS disorders in patients with VZV infections (6-13, 20) ( Table 3).

DISCUSSION
Here, we present a case with MOG-IgG associated LETM triggered by VZV infection. In a subsequent retrospective study of 59 patients with VZV infection and neurological involvement; however, we did not found MOG-IgG in any patient (including 15 with VZV encephalitis/myelitis). MOG-IgG are more often present in children than in adults and are associated with a variable clinical spectrum. Typical clinical presentation of MOGAD, particularly in children, is an acute disseminated encephalomyelitis (approximately 50%), whereas in adults myelitis (up to 30%) or optic neuritis (up to 50%) are more common (14,(26)(27)(28). Similar to our case, MOG-IgG associated myelitis is characterized in the MRI by longitudinally extensive T2 hyperintense lesions affecting mainly the grey matter and lack of contrast enhancement (29). MOG-IgG case reports showing an association between MOGAD and VZV infection are rare. Two case reports   Table 3). In only one patient, the VZV DNA PCR result was available and reported as positive. In our case, the VZV DNA PCR result was negative, which may have been due to the preceding acyclovir therapy (6 days). However, elevated WBC count and a highly increased VZV ASI confirmed the diagnosis. In a group of 10 immunocompetent patients with VZV infection-related myelitis, MOG-IgG was present in one patient (20). This patient relapsed and fulfilled the seronegative NMOSD criteria during follow-up. In contrast, our patient showed nearly complete recovery without further relapses, and MOG-IgG was undetectable after eight months. Approximately 35% of patients with MOGAD have a relapsing disease (14). Although persistent MOG-IgG positivity is only a moderate marker for relapsing disease with a positive predictive value of approximately 60%, a conversion to undetectable antibody reliably predicted a monophasic disease course in approximately 90% of cases (14). Due to limitations such as a lack of prospective clinical trials in MOGAD and established standard test criteria conversion of detectable to undetectable MOG-IgG is currently not a reliable marker for treatment decisions. However, as a) only approximately one third of the patients with MOG-IgG relapse, b) MOG-IgG was negative during follow-up, and c) due to the known viral trigger, we decided not to start a disease modifying or immunosuppressive treatment. In addition to MOG-IgG, several case reports have described an association of AQP4-IgG with VZV infection ( Table 3), we identified 9 further reports of AQP4-IgG associated CNS inflammatory demyelinating disorder related to a VZV infection. In synopsis with the MOG-IgG associated cases, eleven patients out of twelve presented with LETM (the one remaining case was MRI-negative myelitis), LETM seems to be a typical clinical presentation of these rare associations. Of particular importance, for eight patients, there was information available that indicated that the NMOSD (1/8 MOG-IgG positive, 7/8 AQP4-IgG positive) criteria were fulfilled, and that relapses occurred in at least six patients. Therefore, in the rare clinical presentation of LETM triggered by a VZV infection, screening for MOG-IgG or AQP4-IgG has therapeutic implications. In contrast to cases in whom MOG-IgG are detected, treatment with a diseasemodifying therapy should be considered if AQP4-IgG is detected. The pathophysiological basis of the association between VZV infection and MOG or AQP4 antibody-associated associated LETM is unclear. In the majority of the reported cases, CSF VZV DNA PCR results were negative ( Table 3), and a direct viral invasion of the spinal cord seems unlikely, although pathological data are missing. These data are consistent with the retrospective case series of immunocompetent individuals with VZV myelitis published by Wang et al. (20). Four out of 11 patients fulfilled the NMOSD criteria, and despite immunosuppressive treatment in the two relapsing patients, no VZV reactivity was observed. Given the rising number of cases with the presence of MOG-IgG or AQP4-IgG and the typically delayed onset of neurological symptoms ( Table 3) after the rash, immune-mediated genesis seems likely. The mechanisms suspected to be involved in triggering autoimmunity after infection are molecular mimicry, bystander activation, epitope spreading, and the release of cryptic antigens (30). A possible hypothesis for MOG and AQP4 antibody-associated autoimmunity triggered by a VZV infection is that the VZV infection causes a breakdown of the blood-brain barrier, as indicated by the common finding of an elevated CSF/serum albumin ratio in herpes zoster (31). Subsequently, CNS antigen is released into the periphery, which induces an immune reaction against self-antigens by autoreactive B and T cells.
A limitation of our study is the retrospective design and small number (n=15) of patients with myelitis, encephalomyelitis, or encephalitis. However, data specifically excluded a nonspecific bystander reaction, as patients with VZV infection without parenchymal involvement were negative for MOG-IgG (n=44). As CSF analysis of MOG-IgG improve the sensitivity by 7%, another limitation is that MOG-IgG was only tested in patient sera (32).
Overall, we showed that the presence of MOG-IgG is a rare finding in patients with a VZV infection complicated by CNS demyelinating-inflammatory diseases. Nevertheless, due to

DATA AVAILABILITY STATEMENT
The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

ETHICS STATEMENT
The studies involving human participants were reviewed and approved by Medical University Innsbruck. Written informed consent to participate in this study was provided by the participants' legal guardian/next of kin. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.

AUTHOR CONTRIBUTIONS
FDP conceptualized the study, collected data, case analysis, statistical analysis, drafted the manuscript, and revised the manuscript for intellectual content. PM collected data and revised the manuscript for intellectual content. KB collected data and revised the manuscript for intellectual content. MA collected data and revised the manuscript for intellectual content. AB collected data and revised the manuscript for intellectual content. TB case analysis and revised the manuscript for intellectual content. GB collected data and revised the manuscript for intellectual content. PR MRI analysis and revised the manuscript for intellectual content. KS collected data and revised the manuscript for intellectual content. AZ collected data and revised the manuscript for intellectual content. FDe case analysis, conceptualized the study, and revised the manuscript for intellectual content. MR conceptualized the study, and revised the manuscript for intellectual content. HH conceptualized the study, collected data, case analysis, statistical analysis, drafted the manuscript, and revised the manuscript for intellectual content. All authors contributed to the article and approved the submitted version.

FUNDING
This study was funded by a research grant from the Austrian Science Fund (FWF projects P32699, MR). His institution receives payments for antibody assays (MOG, AQP4, and other autoantibodies) and for MOG and AQP4 antibody validation experiments organized by Euroimmun (Lübeck, Germany). HH has participated in meetings sponsored by, received speaker honoraria or travel funding from Bayer, Biogen, Merck, Novartis, Sanofi-Genzyme, Siemens, Teva, and received honoraria for acting as consultant for Biogen and Teva.
The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.